1. Field of the Invention
The present invention relates to a miniature DC (direct current) brushless motor having a radial air gap and a single coil with axial winding.
2. Description of the Related Art
U.S. Pat. No. 5,289,089 to Aoki issued on Feb. 22, 1994 discloses a small sized DC motor at a high torque and with a high efficiency to reduce noise generation and suitable for forming in an integrated circuit. Although the Aoki patent solves the problems of a conventional motor drive (see FIG. 2 of said U.S. patent), the axial thickness of the stator cannot be reduced to meet the requirement for a miniature motor shaft. This is because the winding for the stator coil is radial, as shown in FIGS. 6 and 7 of the drawings. FIGS. 6 and 7 ti respectively show a four-pole stator 100 and a two-pole stator 100 constructed in accordance with the teaching of Aoki in said U.S. Pat. No. 5,289,089. In FIG. 6, the stator 100 includes four arms (poles) 102 extending outwardly from a central axial hole 101 thereof while in FIG. 7, the stator 100 includes two arms (poles) 102 extending outwardly from a central axial hole 101 thereof. The winding procedure for the radial coil is time-consuming, as the coil must be wound around each arm 102 at one time without interruption. In addition, the distribution of the magnetic field is not uniform. There is, therefore, a need in miniature DC motors with minimum axial thickness and high motor power for an easy winding procedure that can be accomplished at one time without any interruption.